Blender 2.8 One God Ray Effect
In the View Layer Properties just enable in the Light Settings In
EEVEE: Light &gt; Volume &gt; check Light.
Cycles: Light &gt; Volume &gt; check Indirect.
Now when you click Render you will have a combined Pass and a Light Pass/Indirect Light Pass. It looks black and white because the volumetric light is isolated.
That Means you now have to disable all lights except the light used for the godray effect.
Then you can use the rendered Light Pass (with the isolated Direct Light from the godray) to mix it in the Compositor with the rendered scene (without any Volumetrics and all lights enabled excepts for the Godray Light).